The invention relates to an optical interferometer, and to an interferometer which comprises such an optical interferometer.
An optical interferometer is used to split an output beam using a beam splitter device into at least one first and one second sub-beam; the two sub-beams are guided, at least in regions, through separate optical tracks and the two sub-beams are finally superposed again in order to form interference. Interferometers in embodiments such as e.g. the Mach-Zehnder interferometer or the Michelson interferometer are known.
Here, the invention relates to interferometers which are embodied as heterodyne interferometers. Such heterodyne interferometers comprise at least one optical frequency shifter in the beam path of the interferometer, typically in the beam path of one of the at least two sub-beams.
Such interferometers are used, in particular in metrology, for precisely determining lengths or for determining the movement or vibration of an object.
EP 0 448 751 B1 has disclosed a heterodyne interferometer with a lithium niobate crystal. The interferometer comprises a polarization-rotating converter, which shifts frequencies in the process. In this case, an output beam is split, in particular by two acousto-optic components, into two sub-beams with approximately the same intensity but different polarizations, which sub-beams are separated by a polarization splitter.